In general, a gasoline engine particularly requires knock control in order to maximize engine performance. Therefore, an engine control unit (ECU) of a vehicle determines whether engine knocking occurs by checking a signal detected through a knocking sensor, and applies retarded timing when the engine knocking occurs, thus gradually recovering the ignition timing for the knock control.
In the engine knocking, mixed gas in an engine combustion chamber is self-ignited and combusted for propagation of a flame inflamed from an ignition plug. When the knocking occurs, a pressure increase, which occurs by rapid combustion, vibrates a piston and a connector rod to generate noise. Since the vibration of combustion gas promotes heat transfer, overheat and burning of an electrode of the ignition plug or a piston occur when the vibration continues, thereby damaging the engine.
In order to solve the problem, in the related art, engine knocking is prevented by delaying an ignition time when there is a knock signal to gradually advance the ignition timing. However, since the ignition timing needs to be adjusted whenever the knocking occurs, it is impossible to automatically prevent the occurrence of the knocking.
In recent years, an engine control unit has been developed to store a knocking learning value (alternatively, a retarded timing learning value) so as to learn a retarded timing amount when engine knocking occurs. The ECU is configured further to retard the ignition timing when an engine keeps running under the same engine operating condition, and to recover the retarded timing when the knocking stops after a reference period of time elapses.
During controlling of the engine knocking as described above, after the knocking stops after the reference period of time, the engine needs to run for a predetermined time under the same operating condition as when the knocking occurs in order to recover the retarded timing. However, since it is difficult to maintain the engine running for the predetermined time with the same operating condition in an actual driving of a vehicle, for example, when a driving situation or a driving environment changes, it may be difficult to maintain the same operating condition.
For example, if a vehicle travels under a different engine operating condition before a reference period of time has reached, a time duration during which the vehicle travels under the engine operating condition in which the knocking occurs needs be reset.
Therefore, when the retarded timing amount is not recovered during the knock control during the engine running, an excessive delay of the ignition time occurs, thus decreasing an engine torque and deteriorating fuel efficiency.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention, and therefore, it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.